title: Morphological and physiological responses of rice seedlings to complete submergence (flash flooding).
abstract: OBJECTIVE
  Reducing damage to rice seedlings caused by flash flooding will improve the productivity of rainfed lowland rice in West Africa. Accordingly, the morphological and physiological responses of different forms of rice to complete submergence were examined in field and pot experiments to identify primary causes of damage.
  
  
  METHODS
  To characterize the physiological responses, seedlings from a wide genetic base including Oryza sativa, O. glaberrima and interspecific hybrids were compared using principle component analysis.
  
  
  RESULTS
  Important factors linked to flash-flood tolerance included minimal shoot elongation underwater, increase in dry matter weight during submergence and post-submergence resistance to lodging. In particular, fast shoot elongation during submergence negatively affected plant growth after de-submergence. Also shoot-elongating cultivars showed a strong negative correlation between dry matter weight of the leaves that developed before submergence and leaves developing during submergence.
  
  
  CONCLUSIONS
  Enhancement of shoot elongation during submergence in water that is too deep to permit re-emergence by small seedlings represents a futile escape strategy that takes place at the expense of existing dry matter in circumstances where underwater photosynthetic carbon fixation is negligible. Consequently, it compromises survival or recovery growth once flood water levels recede and plants are re-exposed to the aerial environment. Tolerance is greater in cultivars where acceleration of elongation caused by submergence is minimal.
authors.affiliation: Japan International Research Center for Agricultural Sciences, 1-1 Ohwashi, Tsukuba, Ibaraki 305-8686, Japan.
authors.forename: Naoyoshi
authors.initials: N
authors.lastname: Kawano
authors.forename: Osamu
authors.initials: O
authors.lastname: Ito
authors.forename: Jun-Ichi
authors.initials: J
authors.lastname: Sakagami
mesh_terms: D018533:Biomass; D055868:Floods; D012275:Oryza / Q000033:anatomy & histology* / Q000502:physiology*; D018515:Plant Leaves / Q000254:growth & development; D018520:Plant Shoots / Q000254:growth & development; D025341:Principal Component Analysis; D019655:Quantitative Trait, Heritable; D036226:Seedlings / Q000033:anatomy & histology* / Q000502:physiology*